Various synthetic roof and wall coverings are known, such as those formed of elongated thermoplastic panels that are nailed or screwed to a wall or roof support surface in horizontal courses or rows in partially overlapping relation to each other so as to provide a substantially water resistant, protective layer over the support surface. Such panels, which usually are identically molded, are commonly formed with a plurality of rows of simulated building elements, such as shake shingles. Because the panels are relatively large, such as up to eight feet and more in length, they can be cumbersome to handle and install, particularly on vertical wall and steep roof surfaces. Since the panels are identically molded, a panel-to-panel identity also can be easily noticed if the panels are not carefully installed. Leakage problems between adjoining panels can also occur under these circumstances.
Such panels commonly are nailed to the wall or support surface in horizontal courses, beginning with the lower-most course. To enable interlocking engagement between the upper and lower marginal edge regions of vertically-adjacent panels, it is known to provide a plurality of longitudinally-spaced outwardly and downwardly directed interlocked fingers along the upper marginal edge region of the underlying panel which are engaged by a bottom rail formed on the underside of the overlying panel as an incident to upward positioning movement of the panel. Due to the size of the panels it can be difficult for the installer to engage all of the fingers with the upturned rail, with any missed fingers causing an unsightly bowing of the overlying panel, which both detracts from its appearance of the finished wall covering and makes it more susceptible to water entering the juncture between the panels.
Even when the panel is properly positioned, it can be difficult for the installer to properly hold and maintain a panel and at the same time nail or screw it to the wall surface. Because the upturned interlock rail on the overlying panel extends across a rear side of the simulated shake, even with careful molding, a transverse line of the rail can sometimes be faintly observed from a front side of the panel, which again detracts from the natural appearance of the wall covering. The upturned rail also can undesirably capture and retain water that might migrate between the panels, such as during severe weather conditions.